Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pineal indole melatonin suppresses the neonatal rat luteinizing hormone (LH) and follicle-stimulating hormone (FSH) responses to LH-releasing hormone (LHRH), as shown in previous studies from this laboratory. We show in this study that the melatonin inhibition is a selective effect and is not due to general inhibition of pituitary function. The effects of the indole on the responses to thyrotropin-releasing hormone (TRH) and somatostatin (SRIF) and on basal pituitary hormone secretion were examined with cells in culture. Neonatal rat anterior pituitary cells dissociated with collagenase and hyaluronidase were cultured overnight and distributed to 35-mm dishes at the time of use. For examination of melatonin effects on the response to releasing hormones, the cells were incubated for 3 h in control medium or medium containing LHRH (10-9-10-6 M), TRH (10-10-10-6 M), or SRIF (10-9-10-6 M), either alone or in the presence of melatonin (10-8 or 10-6 M). For examination of basal hormone secretion, the cells were incubated for 1.5, 3, 6, 15, or 24 h in either medium alone or medium containing melatonin (10-6 M). Medium and cell lysate concentrations of LH, FSH, thyroid-stimulating hormone (TSh), prolactin (PRL) and growth hormone (GH) were determined by double antibody RIA. As previously, melatonin (10-8 M) significantly suppressed LH and FSH release by all concentrations of LHRH. This concentration of the indole produced maximal suppression of both LH and FSH responses to LHRH. By contrast, melatonin at a 100-fold greater concentration (10-6 M) had no effect on TRH stimulation of TSH or PRL release or on SRIF inhibition of GH release. Similarly, melatonin had no effect on basal release of TSH, PRL, or GH at the times examined. These findings show that melatonin inhibition of the gonadotroph response to LHRH is a selective effect.
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PMID:Selectivity of melatonin pituitary inhibition for luteinizing hormone-releasing hormone. 612 68

Regulation of somatostatin (SS) secretion was studied in an in vitro system using collagenase-dispersed cells from fetal rat hypothalamus maintained in long term monolayer culture. Cultured cells exhibit a measurable basal secretion of immunoactive SS (SSLI) which can be augmented by carbachol, acetylcholine, or oxotremorine. The EC50 for carbachol is about 1 microM. Atropine, but not hexamethonium, antagonizes the action of cholinergic agonists. Cobalt or tetrodotoxin pretreatment diminishes basal secretion and eliminates the response to carbachol. Serotonin, several serotonin agonists, and gamma-aminobutyric acid (GABA) suppress carbachol-induced secretion. The GABA blockers bicuculline or picrotoxinin reverse the effect of added GABA and by themselves also augment SSLI secretion. Picrotin is inactive. The direct response to either bicuiculline or picrotoxinin is prevented by cobalt or tetrodotoxin treatment. These observations are consistent with the presence of a muscarinic cholinergic receptor which acts by a mechanism depending on an action potential and calcium influx to enhance the release of SSLI from neurosecretory cells. The data also support the conclusion that GABAergic transmission occurs within the cultures to tonically inhibit SSLI secretion. GABAergic, cholinergic, and serotoninergic systems may thus interact at the level of the hypothalamus to modulate SS secretion in vivo and thereby influence anterior pituitary release of GH and TSH.
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PMID:Muscarinic cholinergic stimulation of somatostatin secretion from long term dispersed cell cultures of fetal rat hypothalamus: inhibition by gamma-aminobutyric acid and serotonin. 612 32

Pancreatic islets of neonatal were dissociated by collagenase and cultured for 3 days in the presence of Cytodex beads to allow attachment of the cells to these microcarriers. The bead-attached cells were packed in columns and superfused with a low bicarbonate medium using the same method that we had originally developed for dissociated anterior pituitary cells of the rat. The secretion of insulin, somatostatin, and glucagon by the cells was monitored by radioimmunoassays. The cells in the superfusion system responded as expected from experiments with islet and monolayer cultures of rat pancreas in vitro and in vivo. Increasing glucose concentrations in the superfusion medium increased the release of insulin and somatostatin (SS), whereas glucagon secretory rates remained constant or decreased. A dose-response curve was established between insulin release and D-glucose in which the ED50 of D-glucose for insulin was found between 1.5 and 2 mg/ml. The phosphodiesterase inhibitor, 3-isobutyl-methylxanthine (IBMX), significantly potentiated the insulin response to glucose. Various secretagogues such as IBMX, 8-bromo cyclic AMP, and L-arginine increased insulin, somatostatin, and glucagon secretory rates in an expected manner. The superfusion method offers the possibility to investigate the interactions of dissociated A-, B-, and D-cells and the dynamics of hormone release in short- and long-term in vitro experiments. The method is simple and avoids the problems of monolayer procedures, such as clustering of the cells and poor adherence of dissociated pancreatic islet cells to dishes.
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PMID:Superfusion of dissociated pancreatic islet cells attached to Cytodex beads. 613 17

We have developed a new short term in vitro system to examine hypothalamic somatostatin (SRIF) release. Hypothalamic cells were obtained from normal rats after trypsin or collagenase aided dispersion and released immuno-reactive (IR) SRIF which eluted in 3 molecular weight (MW) forms on gel chromatography. The smallest MW form, which constituted the major peak, co-eluted with synthetic cyclic 1-14 SRIF on gel and reverse phase high pressure liquid chromatography (HPLC). After 24 h in culture in medium containing heat inactivated fetal calf serum, cell viability was demonstrated by two techniques, (1) vital staining with trypan blue, and (2) incorporation of 32Pi into phospholipids. SRIF release was also studied at this time which was optimal in terms of responsivity of the cells to depolarizing stimuli. SRIF release increased in a time dependent manner, over 3 h. Membrane depolarization, induced either by potassium chloride 56 mM or ouabain (the Na+, K+-ATPase inhibitor) 10(-6) M or greater, markedly stimulated SRIF release. Incubation at 4 degrees C, or in the presence of EDTA 0.05 M or verapamil, the calcium channel blocker, 50 microM abolished these stimulatory effects. Glucose deprivation was induced by the addition of 2-deoxy-D-glucose (2-DG) to the experimental medium. 2-DG, at concentrations of up to 200 mg%, had no significant effect on SRIF release during incubation periods of up to 1 h.
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PMID:Somatostatin release from dispersed hypothalamic cells - effects of membrane depolarization, calcium and glucose deprivation. 613 93

We studied the release of immunoreactive somatostatin (IR-SRIF) from hypothalamic cells that were obtained from rats and dispersed with the aid of collagenase. Twenty-four hours after dispersion, cells were placed in a column supported by a matrix of preswollen Biogel P2 and perifused. Fractions were collected on ice and subsequently assayed for SRIF. SRIF release was stimulated markedly by potassium depolarization (KCl, 56 mM), by the Na+-K+-ATPase inhibitor ouabain (10(-4) M), and by dopamine at concentrations as low as 10(-11) M. The stimulatory effects of membrane depolarization were calcium dependent and were not observed in the absence of exogenous calcium in the perifusion medium or in the presence of EDTA (0.05 M). Metoclopramide, the dopamine antagonist, abolished the stimulatory effect of dopamine. In conclusion, release of IR-SRIF by dispersed rat hypothalamic cells can be studied in a simple perifusion apparatus. Release is stimulated by membrane depolarization in a calcium-dependent manner and by dopamine at physiological concentrations.
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PMID:Dopamine stimulates somatostatin release from perifused hypothalamic cells. 613 72

A superfusion method consisting of fully recovered, dissociated pituitary cells adhering to Cytodex beads has proved useful in monitoring the dynamics of hormone secretion over time. Male rat anterior pituitaries were dissociated with collagenase and Viokase, then cultured in the presence of Cytodex beads for 3-5 days, during which time the cells attached firmly to the surface of the beads. The bead-attached cells were stable and could be transferred to any vessel without the need for centrifugation or further trypsinization. For this application, the bead-attached cells were packed in a column and superfused with a low bicarbonate buffer requiring no CO2 gassing. Viability was more than 95% after 48 h in the column. The cells responded in a normal physiological manner to hypothalamic releasing and inhibitory peptides. The ED50 was 0.3 nM for somatostatin and 1.2 nM for gonadotropin-releasing hormone. A postinhibitory rebound of GH secretion was observed after the discontinuation of large doses of somatostatin. LH secretion reached maximal levels within 6 min after 10 nM gonadotropin-releasing hormone, but started declining after 2 h of continuous stimulation and dropped close to baseline within 18 h. GH release was significantly increased by prostaglandin E2, 3-isobutyl-1-methylxanthine, and 8-bromo-cAMP. LH secretion increased 5-fold in response to 1 mM 8-bromo-cAMP, but showed little increase during prostaglandin E2 or 3-isobutyl-1-methylxanthine stimulation. The cocarcinogen phorbol myristate acetate (12-O-tetradecanoyl-phorbol-13-acetate) induced secretion of all pituitary hormones and continued to do so for hours after a short pulse. The superfusion system is simple to operate and has proven effective in studying transient phenomena, desensitization, and short term kinetics of secretagogues.
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PMID:Superfusion of rat anterior pituitary cells attached to Cytodex beads: validation of a technique. 615 98

The properties of gonadotropin-releasing hormone (GnRH) receptors were analyzed in isolated pituitary cells prepared by enzymatic dispersion with trypsin or collagenase-hyaluronidase. The initial impairment of LH responses to GnRH in isolated cells prepared by both methods was reversed during culture for 2 days in multiwell vessels. However, specific binding sites for GnRH, assayed by equilibration with [125I]iodi0[D-Ser(t-BU)6]des-Gly10-GnRH N-ethylamide (GnRH-A) were demonstrable in collagenase-dispersed cells, both initially and after 2 days in culture. Cellular uptake of GnRH-A was temperature dependent, with rapid and saturable binding to a limited number of specific receptor sites with high affinity for the labeled analog (Ka = 4.0 +/- 0.8 X 10(9) M-1). These sites showed common binding specificity for GnRH-A and the native GnRH peptide, with significantly lower affinity for the natural peptide (Ka = 2.3 X 10(7) M-1). Other protein and peptide hormones, including ovine LH, ovine PRL, hCG, TRH, somatostatin, and angiotensin II (up to 10(-6) M) did not inhibit binding of GnRH-A to its receptors. Cellular binding of GnRH-A was followed by increased cGMP production and LH release within 10 min. The analog was 50 times more potent than native GnRH in stimulating LH release. The Kact values derived for GnRH and GnRH-A were 0.5 and 0.01 nM, respectively, considerably lower than the Kd values of 50 and 0.25 nM derived from receptor binding analysis. These results indicate that GnRH receptors can be identified in isolated pituitary cells, in which peptide binding is followed by increased cGMP production and LH release. The impaired LH responses in acutely dispersed pituitary cells are not due to the loss of receptor sites but to a reversible postreceptor defect. Occupancy of about 20% of the GnRH-binding sites elicits a near-maximal LH response, indicating the nonlinearity of GnRH-receptor coupling to secretory responses in the cultured gonadotroph.
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PMID:Characterization of gonadotropin-releasing hormone receptors in cultured rat pituitary cells. 625 Jul 93

Perinatal rat islets of Langerhans, isolated and cultured in vitro, were examined following long-term allotransplantation across a major histocompatibility barrier in nonimmunosuppressed recipients. Islets were isolated to varying degrees of purity without the use of collagenase digestion. Newborn bovine serum was a component of the incubation medium and the atmosphere during culture was air: 5% CO2. Islets transplanted without rigorous purification were fully rejected by 14 days posttransplantation. However, if islets were maintained in subculture, permitting their subsequent meticulous purification, no evidence of rejection was observed after 45 days at the kidney subcapsular site. Grafts consisted of morphologically intact islets. The three major endocrine cell types of the islet were identified by immunocytochemical localization of insulin, glucagon, and somatostatin. These results demonstrate that perinatal islets can exhibit altered immunogenicity, as evidenced by prolonged allograft survival, when isolated and purified by the nonenzymic in vitro method.
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PMID:Modification of allograft immunogenicity in perinatal islets isolated and purified in vitro. 642 93

The ability of dispersed islet cells in a perifusion system to secret glucagon and insulin in response to physiologic stimuli was investigated. Normal hamster islets were isolated by collagenase digestion and the cells dispersed by sequential digestion with collagenase and trypsin. Following a 50-min period of equilibrium in buffer with high glucose concentrations (5.0 mg/ml), glucagon secretion was stimulated by glucopenia and subsequently, inhibited by increasing the concentration of glucose. The responsiveness to glucose inhibition was significantly less in dispersed islet cells than in intact islets. However, the dispersed islet cells showed significantly greater response to arginine. Glucagon secretion by dispersed islet cells was stimulated to tolbutamide and epinephrine but somatostatin had no effect. Dispersed islet cell preparations did not augment insulin secretion in response to glucose but did secrete more insulin in response to arginine. Intact islets secreted insulin in response to glucose but not arginine. We conclude that A cells in cell suspension do not need direct contact or an intact intra-islet environment in order to respond to glucose, arginine, epinephrine, or tolbutamide but the extent of response may be influenced by paracrine effects. However, paracrine relationships may be important in determining the response of B cells to secretagogues.
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PMID:Glucagon and insulin secretion by dispersed islet cells: possible paracrine relationships. 675 81

The ability of TSH to stimulate synthesis and release of thyroid hormones in ovine thyroid follicles in vitro depends partially on a synergy with insulin-like growth factors (IGFs). The cellular availability of IGFs may be influenced by the release of several IGF binding proteins (IGFBPs). The purposes of these studies was to 1) further characterize the species of IGFBPs synthesized by thyroid follicles, 2) examine the ability of TSH and cortisol to alter IGFBP gene expression and protein release, and 3) investigate the actions of exogenous IGFBPs on thyroid cell function. Adult sheep thyroid follicles were isolated after collagenase digestion, grown to confluence in Coon's modified Ham's F12M medium (OH) with the addition of transferrin, glycylhistidyl-lysine, somatostatin (3H), cortisol and insulin, and maintained in serum-free test media with or without further supplements for up to 48 h. Conditioned media were analyzed for IGFBP presence by Western ligand blotting, and by immunoblotting using specific antisera against bovine IGFBP-2 and human IGFBP-5. IGFBP mRNAs from follicles were identified by Northern blot hybridization using [32P]labeled complementary DNAs encoding ovine IGFBP-1 or -2, and rat IGFBP-4, -5, or -6. Uptake and organification of Na[125I] were measured by incorporation into trichloroacetic acid-precipitable material. Isolated thyroid follicles synthesized four species of IGFBPs in either 0H or 3H medium as detected by ligand blotting, of sizes 40-46, 34, 28, and 18 kilodaltons (kDa), respectively. The 32 kDa IGFBP was identified immunologically as IGFBP-2, whereas the 28 kDa and 18 kDa species were identified as IGFBP-5. Northern blot hybridization of total RNA from cells in 3H medium demonstrated an IGFBP-2 messenger RNA (mRNA) [1.4 kilobase (kb)], an IGFBP-4 mRNA (2.6 kb), and two IGFBP-5 mRNAs (6 kb and 1.8 kb). No IGFBP-1 or -6 mRNAs were detected. Incubation of cultured follicles with TSH (30-500 microU/ml) caused a dose-dependent decrease in the abundance of all IGFBP mRNAs and released proteins, which were reduced further by TSH together with cortisol (10 nM). When the inhibitory effect of TSH and cortisol was removed, IGFBP-2 mRNA increased within 3 h and was 7-fold greater within 12 h. IGFBP-2 did not appear in the conditioned medium until 12 h after TSH removal, along with the other IGFBP species.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Hormonal regulation and biological actions of insulin-like growth factor binding proteins in isolated ovine thyroid follicles. 750 36


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